Line Boring Metal 3D Print

[jccaclimber]

You can artificially age from T4 to T6 in an oven, if the T4 state wasn’t achieved you will not get anywhere with the extra aging. I had that issue on an extrusion several years ago. The material had to be heated back up and quenched before we could get it to T6.

 

[Novaguy]

Finally got around to machining this piston...decided to start with the oblong wrist pin bores.

View attachment 389475

With a non-circular bore to start with, I turned down the fixture and then filed down 2 sides flat so the piston would just fit on.



Used a 3D printed spacer to tighten the M10 nut against since the back of the wrist pin bore isn't flat. Did one side, then made a 2nd fixture the same way to line bore the other bore.



Then I indicated in the wrist pin to be perpendicular to the OD, then faced off the bottom of the piston skirts. This made a flat feature for the next fixture.



The 2nd fixture was used for turning the OD and ring grooves. It was something like this but using a 3D printed part to hold the wrist pin.







This parting tool was bending like crazy, making tapered grooves...



So I found the best fitting grooving tool for this size and it was an INSIDE grooving tool...Ran the lathe in reverse taking super tiny cuts. The piston still wound itself off the fixture...





Came out halfway decent. The real test is will it actually run in the engine...

 

[Novaguy]

OD on the piston skirts is about 47.978 mm for a 48 mm cylinder bore. The wrist pin bores are out of line about .0011" end to end, but that should work in the short term.

 

[Milland]

Good luck, will be interesting to hear the results. As in, "hear", take video and post to YT.

 

[EPAIII]

Dirt bike / F1 car. I am not so sure I understand the difference.

Oh, wait, when the piston cracks in the race car there will dozens/hundreds of people around. And you would have a trailer to load it on to drive home. When it cracks in the dirt bike you are 100 miles from the nearest road and all you have is shoe leather. Got it!

I hope you accounted for the 3D printed nature of that piston design.

Thanks ...<snip>...

It's an 80cc dirt bike piston for demonstration, not for an F1 car.

 

[Novaguy]

Dirt bike / F1 car. I am not so sure I understand the difference.

Oh, wait, when the piston cracks in the race car there will dozens/hundreds of people around. And you would have a trailer to load it on to drive home. When it cracks in the dirt bike you are 100 miles from the nearest road and all you have is shoe leather. Got it!

I hope you accounted for the 3D printed nature of that piston design.

That's quite an imagination you got there.
Who rides a 1975 XR75 100 miles with a 3D printed piston that may not last 100 ft?

Why is this your comment on a machining forum?...

 

[rcoope]

Thanks for posting the follow up Novaguy. Everyone here really appreciates the "what I did and how it worked out" posts after people chime in with advice. I look forward to seeing how it runs in the XR75 at your local dirt track within a few hundred feet of the truck and maybe a Starbucks nearby.

 

[Novaguy]

Good luck, will be interesting to hear the results. As in, "hear", take video and post to YT.

You'll likely hear the wrist pin play immediately

Thanks for posting the follow up Novaguy. Everyone here really appreciates the "what I did and how it worked out" posts after people chime in with advice. I look forward to seeing how it runs in the XR75 at your local dirt track within a few hundred feet of the truck and maybe a Starbucks nearby.

Usually the OP disappears taking the solution with them. Lots of good suggestions by members here and I wanted to at least show a way it could be approached. If she lasts at WOT for a few seconds, I'll count it as a success lol